Hard, wear-resistant ferrous alloy



United States Patent 3,334,996 HARD, WEAR-RESISTANT FERROUS ALLOY George Foster, Westfield, and Lawrence Mattek, East Brunswick, NJ., and William W. McCaudless, Newtown, Pa., assignors to Xaloy Incorporated, New Brunswick, NJ., a corporation of California No Drawing. Filed Dec. 13, 1966, Ser. No. 601,329 4 Claims. (Cl. 75-126) ABSTRACT OF THE DISCLOSURE A hard, wear-resistant ferrous alloy of from 2.40 to 2.90 weight percent carbon, 0.50 to 1.25 weight percent manganese, 0.25 to 1.25 weight percent silicon, 24.0 to 30.0 weight percent chromium, 1.0 to 2.0 weight percent molybdenum, 0.4 to 1.0 weight percent vanadium, 3.20 to 3.90 weight percent boron, up to 8.0 weight percent nickel, up to 0.05 weight percent phosphorus, up to 0.05 weight percent sulfur, and the balance essentially iron. The alloys are centrifugally cast into linings by placing the same, in cast or melt form, within a tubular steel housing and heating and spinning the housing to form an alloy liner therein.

This application is a continuation-in-part of copending application Ser. No. 342,762 filed on Feb. 5, 1964, now abandoned.

The present invention relates to a ferrous alloy having improved hardness and wear-resistant characteristics, and more particularly to such an alloy desirable for use as a lining for catalytic crackers, plastic extruders, Banbury mixers or other devices requiring hard, wear-resistant linings.

In the following specification all parts and percentages are given by weight, unless otherwise specified.

It is among the objects of the present invention to provide a hard, wear-resistant ferrous alloy suitable for use for apparatus linings or the like, which alloy also possesses improved resistance to corrosion by sulfurous or like atmospheres facilitating its further use in oil well liners or for similar applications in the petroleum industry.

The nature and objects of the invention will be more fully apparent from a consideration of the following detailed description thereof.

The ferrous alloy of the present invention comprises the following elements fused together in approximately the proportions stated below:

Ingredient: Weight percent Carbon 2.40-2.90 Manganese 0.50-1.25 Silicon 0.25-1.25 Phosphorus Up to 0.05 Sulfur Up to 0.05 Chromium 24.0-30.0 Nickel Up to 8.0 Molybdenum 1.0-2.0 Vanadium 0.4-1.0 Boron 3.20-3.90

Iron, balance to make up 100%.

It will, of course, be understood that the ferrous alloy need not contain any of the nickel additive, or any sulfur or phosphorus, which are impurities therein; the expression up to a specified percentage is thus intended to include zero percent of the indicated component. When, for example, the alloys of the invention are employed in petroleum applications, e.g., for liners for oil wells, and are exposed to sulfur-containing compounds, it is preferred to omit nickel from the liner composition.

It has been found that ferrous alloys having composi- "ice tions of the indicated ingredients in the proportions specified above possess hardness characteristics of from about 60 to 70 Rockwell C, which is above the range usually found in conventional hard-surfacing steels.

Furthermore, the indicated ferrous alloys of the present invention provide superior wear-resistance as compared with various commercially available materials utilized for liner manufacture such as (1) ferrous alloys consisting principally of iron and containing from about 0.2 to 6% nickel, 2 to 4% combined carbon, 0.2 to 2.5% boron, up to about 2.5% silicon, up to about 0.1% sulfur and up to about 0.3% phosphorus (see US. Patent No. 2,046,- 913), and (2) nickel-cobalt alloys containing from about 40 to 45% nickel, 40 to 45 cobalt, 6 to 8% chromium, 3 to 4% boron, l to 2% silicon, up to about 1% manganese and up to about 0.5% carbon. The ferrous alloys hereof additionally possess improved corrosion resistance as compared with the ferrous alloys designated (1) above, and improved resistance to sulfurous fumes as compared with the nickel-cobalt alloys designated (2) above.

It is believed that the superior hardness characteristics of the novel alloys of the present invention result, at least in part, from the presence of excess chromiumboride-carbides which provide a reservoir of elemental materials sufiicient to counteract dilution of the metal alloy during melting for liner formation. Moreover, when the alloy composition is fused upon the surface of a ferrous metal housing or other element to form a lining thereon, a diffusion area is formed at the interface with such surface which is usually constituted of a bainitic material. The alloy matrix simultaneously formed is constituted of a partially lamellar structure of transformed austenite, comprising martensite and/ or bainite plus carbides and borides.

The lamellar structures of the alloys of the present invention are markedly distinct from the lamellar pearlite structures found in steels. In the alloys hereof, the lamellar constituent is believed to primarily comprise alternate layers of martensite and/or bainite and carbides. The martensite/bainite constituent is hard, usually having a Rockwell C hardness value of above 40. On the other hand, the alternating layers in lamellar pearlite steels are ferrites and carbides, the former of which are relatively soft, usually having Rockwell C hardness values of below 15. The replacement of the ferrite lamellae by martensite and/ or bainite strata is thus believed to impart increased hardness to the alloy material.

The bainitic interface is very hard and yet ductile and minimizes, if not prevents, peeling of the alloy lining from the surface of the ferrous metal housing. The lamellar condition of the martensite and/or bainite-carbide-boride matrix further improves the hardness-ductility characteristics of the resulting lining. I

It will, of course, be understood that the preceding explanation of the factors to which the improved characteristics of the alloy of the present invention may be attributed is illustrative only, and is not intended in a limiting sense.

The ferrous alloys hereof are, as indicated above, preferably employed in the formation of liners for various devices requiring hard, wear-resistant material-contacting surfaces. Such linings may, for example, be formed on either the interior or exterior surfaces of cylindrical ferrous metal shells 'and the desired devices fabricated therefrom, e.g., as described in US. Patents 2,275,503 and 2,319,657 and copending application Ser. No. 303,313

lining is to be formed, e.g., into the interior of a tubular steel housing. The alloy composition may previously be fused and charged in shot form or in cast and crushed form into the tubular housing.

After capping the ends of the tubular steel housing to contain the charged alloy and prevent atmospheric oxidation, the unit is placed in a furnace containing an inert atmosphere limiting oxidation and thereby minimizing scale formation, and heated at a temperature of from about 2250" to 2500 F. to melt the components. After heating the sealed tube to above the melting point of the alloy composition, i.e., from about 2250 to 2500 F., for up to two hours (depending on the size of the tube), the assembly is removed from the furnace and spun to centrifugally form the alloy lining. Upon cooling the housing, the molten metal solidifies and bonds metallurgically to the steel housing. Thereafter the caps are removed from the ends of the housing and the internal and external diameters desired are finished in customary manner.

The following example illustrates one method of forming wear-resistant liner structures constituted of the ferrous alloys of the present invention.

Example Calculated proportions of pig iron and alloying ingredients were admixed and heated to well above the melting range of the admixed alloys. A portion of the resulting melt was analyzed and found to contain the following:

Iron, balance to 100%.

The melt was thereafter pelletized and the hardness of the pellets measured. The composition was found to have a hardness of 64 to 67 Rockwell C.

The alloy pellets were charged within a steel tube in which it was desired to form a wear-resistant liner. The tube ends were capped and the assembly mounted within a furnace maintained at 2400 F. After 16 minutes the assembly was removed from the furnace and the tube spun at a rate of 1375 r.p.m. to centrifugally form the alloy melt into the desired liner. After cooling to about 1700 F. while rotating, the rotation was terminated and the tube was covered with Sil-O-Cell for a period of 16 hours to effect slow cooling in a manner to induce compressive stresses in the lining alloy. The caps were thereafter removed from the tube. The hardness of the resulting liner was 63-64 Rockwell C.

Ring sections of the resulting lined tube were compressed in the jaws of a vise without evidence of peeling or other failure at the lining alloy-steel tube interface.

It may thus be seen that, in accordance with the present invention, a ferrous alloy having improved hardness and wear-resistant characteristics may be produced.

Various changes may be made in the preceding example illustrating the utility of the alloy hereof without departing from the scope of the invention. Thus, the alloy composition might, for example, be poured directly, as a melt, into a heated cylinder and the cylinder then spun to centrifugally form the desired alloy lining thereof. In view of the above and other possible variations, it should be understood that the preceding description is intended as illustrative and not in a limiting sense.

We claim:

1. A hard, wear-resistant ferrous alloy consisting essentially of the following ingredients fused together in approximately the the proportions stated below:

Ingredient: Weight percent Carbon 2.4-2.9 Manganese 0.5-1.25 Silicon 0.25-1.25 Chromium 24.0-30.0 Molybdenum 1.0-2.0 Vanadium 0.4-1.0 Boron 3.2-3.9 Phosphorus Up to 0.05 Sulfur Up to 0.05 Iron Balance 2. A hard, wear-resistant ferrous alloy consisting essentially of the following ingredients fused together in approximately the proportions stated below:

Ingredient: Weight percent Carbon 2.68 Manganese 0.89 Silicon 0.78 Phosphorus 0.023 Sulfur 0.008 Chromium 26.25 Molybdenum 1.3 3 Vanadium 0.73 Boron 3 .5 1 Iron Balance 3. A hard, wear-resistant liner for a steel housing, constituted of the ferrous alloy of claim 1.

4. A hard, wear-resistant liner for a steel housing, constituted of the ferrous alloy of claim 2.

References Cited UNITED STATES PATENTS 1,493,191 5/1924 De Golyer -l26 1,626,726 5/1927 Field 75-126 2,311,878 2/1943 Schlumpf "75-126 X DAVID L. RECK, Primary Examiner. P. WEINSTEIN, Assistant Examiner, 

1. A HARD, WEAR-RESISTANT FERROUS ALLOY CONSISTING ESSENTIALLY OF THE FOLLOWING INGREDIENTS FUSED TOGETHER IN APPROXIMATELY THE THE PROPORTIONS STATED BELOW: 